Dreams and visions are, in a sense, experiences occupying two opposing sides of a spectrum. According to Wikipedia the visionary state is achieved via meditation, drugs, lucid dreams, daydreams, or art. For as long as human beings have kept records of their experiences, they have described extraordinary occurrences: reveries in which they appeared to receive the thoughts of another person, dreams in which they seemed to become aware of faraway events, rituals in which future happenings were supposedly predicted, and mental processes that were said to produce direct action on distant physical objects.
These purported occurrences may have been instances of phenomena that contemporary parapsychologists call telepathy, clairvoyance, precognition, and psychokinesis. Collectively, they are referred to as "psi" or reported interactions between organisms and their environment in which information exchange or influence has occurred that cannot be explained through mainstream science's understanding of sensory-motor channels. They are regarded as anomalous because they appear to occur beyond the constraints of time, space, and energy. The noted Roman orator Marcus Tullius Cicero wrote a skeptical treatise on anomalous dreams entitled, "On Divination." In his treatise, he pointed out that: (Stanley Krippner)
Those very persons who experience these dreams cannot by any means understand them, and those persons who pretend to interpret them, do so by conjecture, not by demonstration. And in the infinite series of ages, chance has produced many more extraordinary results in every kind of thing than it has in dreams; nor can anything be more uncertain than that conjectured interpretation of diviners, which admits not only of several, but often of absolutely contrary senses.
See also: Booze and dreams, Dreams and brain disorders, Dreams as a source of inspiration, Essential oils, Food and dreams, Hypnagogic state, Neuroprotective agents, Sleeping brain, Sleep deprivation, Weed and dreams